The present invention generally relates to contaminant removal and, more particularly, to apparatus and methods of contaminant removal employing gas-liquid contact and separation.
It is of great interest to control and limit the concentration of carbon dioxide in occupied spaces, including homes, buildings, transportation vehicles, aircraft and spacecraft. Higher concentrations of carbon dioxide in the air are uncomfortable, and studies have shown that the ability of individuals to concentrate or make correct decisions is impaired. It is particularly important to control carbon dioxide concentrations in enclosed vehicles like aircraft or spacecraft. In aircraft, fresh air enters the occupied space as bleed air from the engine, and results in increased fuel consumption. In spacecraft, no fresh air is available, and the cabin air must be preserved in a healthful condition. For aircraft, the FAA limits the acceptable concentration of carbon dioxide to 5000 ppm, while aircraft currently have 1500-2300 ppm. Decreasing the bleed air flow would improve fuel efficiency, but would require a technology to remove carbon dioxide from the air.
High levels of carbon dioxide in the International Space Station (ISS) are resulting in headaches, fatigue and eye degeneration in astronauts. Deep Space Missions lengthen crew exposure to these conditions. Therefore, CO2 removal systems for next generation deep space vehicles are required to maintain a much lower CO2 partial pressure. In addition, deep space vehicles are required to have a lower size, weight, power, and thermal load, and use fewer consumables, while fixing existing safety problems that are apparent in current systems. The maintenance interval of current systems (three to six months) is also required to jump to three years.
Long duration, deep space missions require a more advanced life support system than that used on shorter missions or on the ISS. Crewed missions to Mars are likely to last for over thirty months, and little provision for spares or consumables is possible. There will be four to six crew members and the occupied space will be 65.8 m3 in one configuration.
Carbon dioxide recovery is a critical component of the air revitalization system for such missions. Carbon dioxide must be removed from the vessel atmosphere and maintained below 2 torr (2666 ppm) (calculated at 1 atm) to preserve crew health, and maintain alertness and comfort. This carbon dioxide should not be discarded to space, as it was in shorter missions or as it often is on the ISS, but should instead be converted to oxygen and carbon in order for the oxygen to be recycled back to the cabin. Any significant loss in carbon dioxide entails increases in the amount of oxygen or water required to be brought with the mission. For missions to Mars, some plans include landing on the planet and remaining there for eighteen months, during which the Mars Transfer Habitat remains in Mars orbit, unoccupied. The life support system would remain in an operational ready state during this period able to resume operation with high reliability for the return flight quickly.
As can be seen, there is a need for improved apparatus and methods to remove contaminants from a supply air in environments such as deep space vehicles.